Hybrid Racing Performance Radiator CapThe cooling system of your car is one of the most important parts, without one your engine would be useless in minutes. Many people change the cap for esthetic reasons alone, and while we like things to look good, there has to be a more important reason. What does the radiator cap do? Other than the most apparent reason, allowing you to fill your radiator, the radiator cap is an essential part of the system. As the coolant gets hot, it expands